The invention generally relates to a method and apparatus for applying a treatment medium to a textile web in which the web is resiliently pressed against a stationary surface as the web is passed through a gap.
A method of this nature and a device of this kind are disclosed in DE-OS 33 15 770. In this patent the gap is closed on one side by a protruding application bar that forms an opposing face in which a slot is arranged that extends over the web and from which the treatment medium can be squeezed out. Opposite the slot an oblong cushion is arranged, which extends transversely over the width of the web. The cushion rests against a fixed support on the side facing away from the slot. The cushion is covered by a glide foil, which is fastened on the edge opposing the machine direction. The web is pulled through between the opposing face and the glide foil, with the treatment medium, which flows from the slot into the web, being pressed into the web. Since the cushion extends over the entire width of the Web, and since the pressure in the cushion propagates uniformly, the pressure exerted on the web is uniform over the entire width.
A further device is disclosed in FRP 13 81 081. This patent teaches the formation of a vertical narrow treatment trough, which is filled to a certain height with the treatment medium, and through which the web is led in a downward direction. At the lower end of the treatment trough the sides of the treatment trough parallel to the web adjoin the web on s both sides and are pressed against each other by opposing pressure tubes which act from the outside against the lower portions of the sides. In this patent the opposing face is thus also resiliently elastic, and feed of the treatment medium does not take place at the opposing face, but rather at the height of the fill level in the trough through which the web passes. In the first embodiment the web is pulled between the opposing face and the glide foil and in the second embodiment between the sides of the trough that are pressed against each other. It must, therefore, have a certain tensile strength. In addition, and integral to the function of the known devices, the treatment medium is to some extent pressed or massaged into the web. Thus, web must be able, to some extent, to absorb the treatment medium. Textile webs such as woven fabrics and especially those fabrics With pile are primarily of interest. Fabrics with thicker fleece having sufficient tensile strength can, however, also be processed according to this method. No restrictions regarding the web type exist otherwise.
The apparatus disclosed in DE-OS 33 15 770 has proven useful not only in the dyeing of carpeting, but also in the dyeing of flat woven materials. On some occasions, however, it has been observed that the application of the treatment medium is very sensitive to the pressure exerted on the web when it passes the slot. If the pressure rises in a particular site, the web in this location receives noticeably less treatment medium. This effect can be observed especially when materials with pile are used because the volume of the pile is reduced by compression and volume, which could absorb the liquid is eliminated in the process because the material is compressed, is no longer as absorbent as before. The two effects, thus, overlap and relatively slight pressure differences result, for example, in readily noticeable differences in shade and saturation of color when liquid treatment media are used. This leads to problems in the uniformity of dyeing especially at the edges of the web where uniformity of pressure sometimes cannot completely be ensured and where, furthermore, the web for reasons of structure and selvedge absorbs the liquid dye differently than in the web middle even if the pressure is uniform.
The invention, therefore, is directed to the problem of, on the one hand, ensuring treatment which is uniform over the web even if absorption of the treatment medium by the web varies, and on the other hand, advantageously utilizing the recognized sensitivity of the method to differences in pressure for the purposed of imprinting patterns on the web.